Real-Time Magnetic Resonance-Guided Endovascular Repair of Experimental Abdominal Aortic Aneurysm in Swine
Venkatesh K. Raman, MD*,
Parag V. Karmarkar, MSc*, ,
Michael A. Guttman, MSc ,
Alexander J. Dick, MD*,
Dana C. Peters, PhD,
Cengizhan Ozturk, MD, PhD*,
Breno S.S. Pessanha, MD*,
Richard B. Thompson, PhD,
Amish N. Raval, MD*,
Ranil DeSilva, MBBS, PhD*,
Ronnier J. Aviles, MD*,
Ergin Atalar, PhD,
Elliot R. McVeigh, PhD and
Robert J. Lederman, MD*,*
* Cardiovascular Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, Bethesda, Maryland
Laboratory of Cardiac Energetics, Division of Intramural Research, National Heart, Lung, and Blood Institute, Bethesda, Maryland
Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland
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Figure 1 Active-stent endograft. (A) Components of homemade active endograft, constructed from 0.009-inch nitinol wire and expanded polytetrafluoroethylene graft material. (B) Completed one-channel active-stent device mounted on a 5-F catheter and constrained within a 10-F nylon sheath (arrowhead). Matching tuning circuitry is housed in a separate box (arrow).
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Figure 2 Schematic of endograft designs. (A) Unmodified commercial device imaged on the basis of intrinsic magnetic susceptibility (signal void). (B) Homemade endograft device with active opposed loop solenoid coils as markers delineating proximal and distal stent edges. (C) Homemade endograft device with active stent connected to delivery system shaft by a detachable cable that, after deployment and removal of the delivery catheter, renders the stent inactive. (D) Homemade endograft device with active stent as described in (C) and second active marker composed of a multilooped coil on the delivery shaft just beyond the distal stent edge.
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Figure 3 Real-time multislice imaging and three-dimensional rendering during endograft positioning. In the left column, real-time magnetic resonance imaging multislice axial, sagittal, and coronal images shown simultaneously facilitate precise device positioning. Concomitant three-dimensional rendering on the right integrates multislice information. Positioning three axial slices at the caudal renal artery origin, the middle of the aneurysm, and the aortic bifurcation, respectively, allows simultaneous capture of the most important anatomy for device placement. The coronal and sagittal slices provide an overall "bird’s eye" view of the aorta. Orientation markers indicate: S = superior, I = inferior, A = anterior, P = posterior, R = right, L = left. Blue arrow indicates aneurysm.
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Figure 4 Stent strut apposition. (A) Fast spin echo image shows nitinol stent well apposed to target proximal infrarenal aorta (arrows show signal void from stent struts). (B) Spin-echo axial image at level of aneurysm, showing excluded sac (dashed outline). Orientation markers as in Figure 3.
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Figure 5 Magnetic resonance angiogram (maximum-intensity projection) before and after endograft delivery. (A) Conventional contrast-enhanced magnetic resonance angiography shows infrarenal abdominal aortic aneurysm after balloon overstretch. (B) Abdominal aortic aneurysm is excluded by nitinol endograft (causing luminal artifact). Orientation markers as in Figure 3.
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Figure 6 Phase-contrast flow assessments before and after endograft deployment. Axial overlays of in-plane (vector flow map) and through-plane (color map) flow within ruptured experimental aneurysm. Before endovascular repair, there is marked turbulence and evidence of retrograde flow (blue) within the aneurysm (dashed outline). The vena cava is collapsed in this hemorrhagic state. Laminar flow is restored after endograft (dashed outline) deployment. Solid lines border vena cava, identified on cine loops by constant nonpulsatile flow. Orientation markers as in Figure 3.
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